diff --git a/cstp.c b/cstp.c
index 42b70c85..d2fd4a62 100644
--- a/cstp.c
+++ b/cstp.c
@@ -238,6 +238,7 @@ static int start_cstp_connection(struct openconnect_info *vpninfo)
 
  retry:
 	calculate_mtu(vpninfo, &base_mtu, &mtu);
+	vpninfo->cstp_basemtu = base_mtu;
 
 	reqbuf = buf_alloc();
 	buf_append(reqbuf, "CONNECT /CSCOSSLC/tunnel HTTP/1.1\r\n");
@@ -484,6 +485,8 @@ static int start_cstp_connection(struct openconnect_info *vpninfo)
 					     colon);
 				return -EINVAL;
 			}
+		} else if (!strcmp(buf + 7, "Base-MTU")) {
+			vpninfo->cstp_basemtu = atol(colon);
 		} else if (!strcmp(buf + 7, "MTU")) {
 			int cstpmtu = atol(colon);
 			if (cstpmtu > mtu)
diff --git a/openconnect-internal.h b/openconnect-internal.h
index 5a6d6094..10cc909a 100644
--- a/openconnect-internal.h
+++ b/openconnect-internal.h
@@ -566,10 +566,11 @@ struct openconnect_info {
 	char *ifname;
 	char *cmd_ifname;
 
-	int reqmtu, basemtu;
+	int reqmtu, basemtu; /* Local static configured values */
 	const char *banner;
 
 	struct oc_ip_info ip_info;
+	int cstp_basemtu; /* Returned by server */
 
 #ifdef _WIN32
 	long dtls_monitored, ssl_monitored, cmd_monitored, tun_monitored;